The present invention relates to a method for recording the nuclear magnetic resonance in selected areas of a body for the purpose of representing body cross-sections in the form of images (NMR tomography), in which the nuclear spins of a selected type present in the area of one plane of the body are subjected to a superimposed gradient field varying in the selected cross-sectional plane, and selectively excited, whereupon the induction signals supplied by the excited nuclear spins are processed by calculation to obtain image signals.
The cross-sectional images obtained by NMR tomography represent substantially the density distribution of the nuclear spins of the selective type in the cross-sectional plane. But the signal amplitude responsible for the light intensity of the individual image points depends not only on the density of the excited nuclear spins, but also on their state of excitation. Further, the image quality is affected to a quite considerable degree by unavoidable noise signals. There are, consequently, considerable elements of uncertainity in the information content of images of body cross-sections obtained by NMR tomography, and the images obtained are not of the desirable quality.
Accordingly, it is an object of the present invention to improve the known methods used in NMR tomography to increase the information content and the quality of the images obtained.